1. Field
The present disclosure relates to zoom lens systems, interchangeable lens apparatuses, and camera systems.
2. Description of the Related Art
In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems realize: taking of high-sensitive and high-quality images; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Meanwhile, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement.
Zoom lens systems having excellent optical performance from a wide-angle limit to a telephoto limit have been desired as zoom lens systems to be used in interchangeable lens apparatuses. For example, various kinds of zoom lens systems have been proposed, each having a multiple-unit construction in which a positive lens unit is located closest to an object side.
Japanese Laid-Open Patent Publication No. 2011-232624 discloses an optical imaging system having a four-unit construction of positive, negative, positive, and negative, in which zooming is performed by moving the respective lens units from a wide-angle limit to a telephoto limit, and the first lens unit is composed of two lenses, a positive lens and a negative lens.
Japanese Laid-Open Patent Publication No. 2011-197471 discloses a zoom lens system having a six-unit construction of positive, negative, positive, negative, negative, and positive, in which zooming is performed by moving the second lens unit, the fourth lens unit, and the fifth lens unit from a wide-angle limit to a telephoto limit, and focusing is performed by moving the three lens units that are moved in zooming.
Japanese Patent No. 4802598 discloses an optical imaging system having a five-unit construction of positive, negative, positive, negative, and positive, in which zooming is performed by moving the respective lens units from a wide-angle limit to a telephoto limit, and the first lens unit is composed of two lenses, a positive lens and a negative lens.